Smart windows of opportunity

Photochromic shades

Glasses that automatically change to a darker shade when the sun gets out and back to light when clouds appear. It is such a practical application of what is called a photochromic reaction. Why not use the same material for windows in office buildings and houses? At the Faculty of Applied Sciences they are researching if they can scale things up. Professor Dr. Bernard Dam explains about their findings.

Discovery of new material
“My field is functional thin film materials science. I want to find relations between growth, (defect)structure and physical properties in relation to their application. In the case of finding the right application for ‘self-shading’ windows it is all about the properties of the material. To avoid corrosion from weather and other external factors the film needs to be applied on the inside of a window. However, for a photochromic reaction to take place you need a high level of UV light. Glass windows simply do not let enough in. So up to now, the application was not feasible.


Together with fellow scientists in Oslo we have recently discovered by chance a new material that does not need UV light. It’s promising, but there is a lot research to be done. First we need to understand better why this material behaves in the way it does. We need to find out why it reacts to a change in light intensity, what conditions it needs to react and how to speed the process up. At the moment the material changes fairly quickly to a darker shade, but it takes a couple of hours to brighten up again. In countries with very changeable weather, such as in the Netherlands, this would not work. Also being able to influence the contrast would increase the usability. When we understand the material better, we will be able to control it better. Independent of the eventual practical application and bringing an actual product to market, I am driven by finding a scientific explanation and exploring this new material. Smart windows are not just another gadget, but could play a vital role in reducing the energy consumption of buildings. To counter global warming, energy reduction is as important as finding sustainable energy sources. Developing new technology for this purpose is an important driver in my work.

Valuable collection
This photochromic process has a link with the basic technology of photographic emulsions. The TU Delft Library has a valuable collection of books that describe the classical photographic process in great detail. These are reliable sources including references which again lead to other research and related articles. Of course there is also a lot of information online. However, unfortunately, the library does not provide excess to all journals relevant to sustainability. The procedure to request specific articles through the official channels of the Library takes time. From request to access usually takes three days, which is not very practical if you need to get on with your work. It would be helpful if improvements could be made here.”

Publications on photochromic shades: Photochromism of rare-earth metal-oxy-hydrides, F Nafezarefi, H Schreuders, B Dam, S Cornelius,  Applied Physics Letters 111 (10), 103903 [  ]

Library information box

In the past the Library had many subscriptions to complete journals. There has been a change in policy based on financial considerations. It is more cost efficient to provide requested single articles, than an entire journal from which not the entire contents are needed. So before the Library takes a subscription on a new journal, we want to be sure that it is really necessary. Therefore we will talk with faculty library-committees to decide whether a subscription is justified or not, based on various user-statistics. In the meantime we provide articles (free of charge). The delivery of an article from an electronic source takes less than a day. A photocopy of an article in a paper journal may take longer, especially if it has to come from abroad.

While nowadays there is a lot of content being published open access, there is still a lot of scientific literature subscription based, behind the paywall. Due to initiatives from organizations or publishers, different solutions were launched for finding and accessing full-text articles whenever they can be backtracked via their DOI. New tools to browse preprint articles appeared for finding these articles. Find out more in the blog post ‘The open access road to content‘ by Library RND engineer and trend watcher Nicoleta Nastase.

Sustainable solutions
On a larger scale Bernard is coordinating a research programme into e-refinery . Where the chemical industry is now still heavily relying on fossils fuels for energy, a campus-wide team (TBM, TNW, 3ME) is looking into new sustainable solutions. Together they are designing a plan for the electrification of the chemical industry. More on this programme in the next issue of the Library Online Magazine

More information:

Bernard Dam
Han Heijmans Manager Library Research Services on the TU Delft Library resources and collection

Author: Marieke Hopley
Photography: Marcel Krijger

Don’t want to miss the next edition? Subscribe here!

TU Delft Library